Process of purifying sugar juices



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or seen, rnarirroiaa or awaii incomes @l EWRIFZHTG SUGAR Juices This invention relates no processes of puriiying sugar juices and it comprises a process vlerein raw juice, sucli as that obtain-eel 'rom sugar cone or beets, is treated with an icicl to increase the hydrogen oonceniration of the juice to a point at which non-su ars are thrown out Oll'llllfi solution and the mixre oi juice and insoluble non-sugars then bjeciezl to centrifugal separation; it "furcomprises a process wherein the ev sugar juices created. with an acicl clie mixture non-sugars centrifuged above anal the clear liquor coming from *ifuge further oi remaining 2 993.11 gely oil an jclce is a corneqceous solution oi sable nil non-crystalc and inorganic as non-sugars, complex albuminous ls o1E-= cellulosic roulerials, unrls, kc. ll: is practically impossible icc any significant ciysta li ation by be clown raw sugar juice because the nonare "present inhibit cry'slaL liza sion, n of the sugar industry has been to remove all of the non-sugars Without clessro log or otherwise losing any oi"- the svsilaole sugar". it were possible lo re= move all of the non sugais Without loss of sugar in solution a great deal more sugar coulrl be oblainefi rorn a ion of sugar or born a con ol juice extracted theremore;

Generally li alkalinity order to iorro insoluble co compoumis or "lhe non-sugars, But the cipiiate or msolubl-e subslsnces, or

scores olclsinccl manner is clificulc lo filter in the col-filo Heat lies bee rosortecl ,laow

unxl it necessary so lune llie juices to a- .applicatlon files December 53,3, 198%. Serial No. 50%,11.

ever, tends to return the non-sugars to the solution because their calcium compoumls decompose to some extent When heated. Fur-= ibermoreg the problem is complicateil by the iacl; that lime itself forms insoluble comcc pounds, such as calciun sucrose, with the very sugar it is desired to obtain and this of course constitutes aloss of available sugan.

When glucose is present in the juice cal cium compounds thereof may also be formed, so especially ii" the alkalinity exceeds pll-ll 9? to M3. Calcium-glucose compounds when beatccl to 55 C. or higher decompose rapidly giving viscous and dark colored decomposition products which, if present in large quautias lies, make she manufacture of raw sugar (lificult.

So, in order to avoicl the foregoing (iisaob vantages in heating a highly liniecl juice say one limecl lo pH 4 it is customary to carbonm ace the liznccl juices until the alkalinity been reduced, even to almost neutrality cool in this Way obtain a precipitate of calcium carbonate which carries down with it some of 'tlie non-sugars. Without resorting to carwe bonation it is practically impossible to filter s cold highly limecl juice. But carbonation presents disadvantages because some new sugars are thrown oul of solution only at high alkalinity, say pH 10 to 14 aml carbons co Lion since it sole to decrease the pH, teruls to return these non-sugars to the solution, At best, prior practice has been unsatisfactory in many respects.

OUll riefecat cn that is, purification with as out resort to vbeating, is most desirable; ii, has never been practically realizecl because the insoluble-lime compounds either cancel; be filtered at all or cannot be filtered enough fro a a colcl limerl juice.

in my "copenfiing application Sen Ne 8,487, July 8, 1930 l have described a pro cess wherein cold defecation is rendered pra lical and in than; process lime the juices in lo-e colrl auri then separate lshe insoluble lime as compounds in a centrifuge. This process enables use to avoid beating the juices ancl co avoirl excessive carboualoion of the limecl juices and, so far as i am aware, ll am the to have described the use of a centrifuge ice at this particular point in the process. By it, I am enabled to greatly lessen the cost of purifying raw sugar juices, to greatly speed up the time required for purification, to obtain an increased yield of sugar and to ob tain a better quality of sugar.

In,the present invention, I systematically control the hydrogen ion concentration of the juices to be purified in such a way that even greater purification of the raw juices is realized. I depart from the process described in the aforesaid copending application and from any prior practice, in that I first treat the raw sugar juices with an acid to increase the hydrogen ion concentration of the juice. I'have found that many of the nonsugars are niore easily precipitated or rendered insoluble by increasing the hydrogen ion concentration rather than decreasing it, the latter being the method described in the copending applica tion referred to. These compounds, insoluble in acid solution, cannot be filtered in the cold and that is probably one of the reasons why the prior art has not considered any simple acidification process useful. acid juice to fiocculate the insolubles cannot of course be done because sucrose is converted to dextrose and levulose. This is commonly referred to as inversion and it proceeds with great rapidity when an acidified sugar solution is heated.

However, I have further found that the insoluble non-sugars resulting from acidification of the raw sugar juices can be separated in the cold by means of'centrifugal separation and when using this method of separation I can separate the non-sugars thrown out of an acidified solutionwithout dificulty and thus avoid heating.

This preliminary acidification treatment coupled with centrifugal separation without heating the juices constitutes the primary feature of the present invention and is tohe distinguished from certain prior processes wherein raw sugar juice is treated with sulfurous acid to bleach the juice. In this prior practice, the-acidified juice'is always limed after the acid treatment and before it is filtered. This is necessary in order to filter the juice because the insoluble substances thrown out of the solution by means of the 'sulphurous acid cannot be separated therefrom merely by ordinary filtration. The juice acidified with sulfurous acid cannot of course be heated in order to coagulate the precipitate since that would result in an inversion of the sugar which must be avoided. Accordingly, when using sulfurous acid in the purification of sugar juices, prior workers have always found it necessary to lime the acid juices to that point where the juices 'can be heated, and the precipitate thus flocculated, without inversion of place.

Incontrast to this prior art practice, I

the sugar takin g igeemaa acidify the juices and then separate the insoluble precipitate from the unheated acidified juices by centrifugal separation. I do not add lime prior to the separation step, and I do not heat.

After obtaining a clear acidified juice which is free of non-sugars rendered insoluble by the addition of acid I can then continue the purification of the juice in various wags. dvantageously, I decrease the hydrogen ion concentration of the centrifuged acidified juices by adding lime thereto until non-" lization of the sugar therein. Heating an More specifically, I can proceed as follows To a ton of raw sugar juices, either cane or beet, I add sulphurous or sulphur dioxide acid until the juice contains about 0.05 milligrams of free sulphur dioxide per liter. This is roughly equivalent to a pH value of about 3.5. The pH value given is merely illustrative and is not to be taken as an absolute for the reason that sugar juicevaries and the amount of acid added must be governed largely by the character of the raw juice. In practice, the sugar house operative will determine the best hydrogen ion concentrationfor the particular juice he is to purify having regard to the temperature of the juice, its constituents and itsnatural acidity. Generally speaking the limits" are about pH 2.0 to pH 5.0. Within this range, non-sugars rendered insoluble by the presence of a high hydrogen ion concentration are thrown out of most raw sugar juices.

Without heating the juices, I then pass the acidified solution to a centrifuge, advantageously of the well known Kopke type. In the centrifuge, the insoluble non-sugars are separated from the acidified juices. I also am enabled to remove much of the nonsugar material including cellulosic material such as bits of stalk, leaves, etc. These substances, were they not removed at this point, would tend to gelatinize in the subsequent steps. Freeing the juices of cellulosic material prior to any liming operation is one of the important features of this invention since it makes it possible to realize cold defecation as will be more fully described. Wax and ceresin, both of which inhibit the filtration of ordinary cold limed juices are also removed.

meanest solutions. One of the @unex ected results in my process is that the aci ified juice com ing from the centrifuge can, upon being lirned, be filtered cold whereas heretofore it has always been necessary to heat the limed juice to C. or more in order that it mi ht be filtered. This newresult is largely us to the fact that the solution is free of cellulcsic materials and wax, as well as a part of the soluble non-sugars all of which prevent the ordinary filtration of a. cold, limed uice.

Alternatively, I can lime the acidified clear juice coming from the centrifuge to a-very high degree say an alkalinity of pH 12 to 14, filter in the cold, and then carbonate the juices to lower the hydrogen ion concentration to about neutrality. After separation of the precipitate of calcium carbonate and decolorization, the solution is ready for concentration. It should be noted that in this alternative method, I am filtering a highly limed juice prior to carbonation. This-is new in the art.

Various other ways of continuing the urification of the clear, acid juice coming rom the centrifugal after the first separation of non-sugars will be apparent to those skilled in the art.

During the acidification step in m process, it is advanta cons to have a bu er sub stance present, %his is particularly so when sulfurous acid or sulfur dioxide is used to acidify'the juice and in this case I first add a small amount of lime in quantity quite insignificant as regards purification of the juice and then treat the juices with sulfurous acid until the acidity is the best for the se aration of the non-sugars rendered insolu la in acid solution. in this case the lime reacts with the sulfur dioxide to form calcium As stated, I regard the essential features of'rny invention to reside in the initial steps of acidifying the juices in the cold and then jcentrifu ally separating the insoluble substances ironi the juices whereby a preliminarily purified juice is obtained which can be limed and filtered cold, inother words defecated without the application of heat. However, it is to be understood that my in- .then centrifugall vention can be used in conjunction with yarious processes of purifying sugar and that the subsequent treatment of the acidified clear juice coming from the centrifuge can be carried out in other ways than those specifically described.

What is claimed is:

1. The process of freeing sugar juices from non-sugars therein which includes acidifying an unlimed raw sugar juice, which contains substantially all of the non-sugars of an unpurified raw juice, with sulfur dioxide to increase the hydrogen ion concentration thereof and to render non-sugars insoluble and separatig the insoluble non-sugars from t e unheated acidified juice.

2. The process of freeing sugar juices from non-sugars therein which includes acidifying an unlimed raw sugar juice, which contains substantially all of the non-sugars of an unpurified raw juice, with sulfur dioxide until the juice contains about 0.05 milligrams of free sulfur dioxide per liter to increase the hydrogen ion concentration thereof and to render non-sugars insoluble and then centrifugally separatig the insoluble nonsugars from the unheated acidified juice.

3. The process of freeing sugar juices from non-sugars therein which includes acidifying an unlimed raw sugar juice, which contains substantially all of the non-sugars of an unpurified raw juice, with sulfur dioxide to increase the hydrogen ion concentration thereof and to render non-sugars insoluble, centrifugally separating the insoluble nonsugars from the unheated acidified juice and then decreasin the hydrogen ion concentrationof the juice to render remaining nonsugars insoluble.

4. The process of freeing sugar juices from non-sugars therein which includes acidifying an unlimed raw sugar juice, which contains substantially all of the non-sugars of an un purified raw juice, with sulfur dioxide until the juice contains about 0.05 milligrams of free sulfur dioxide per liter to increase the hydrogen ion concentration thereof and to render non-sugars insoluble, centrifugally separating the 1nscluble non-sugars from the unheated acidified juice andthen decreasing the hydrogen ion concentration of the juice to render remaining non-sugars insoluble.

5. The process of freeing sugar juices from non-sugars therein which includes acidifying:

an unlimed raw sugar juice, which contains substantially all of the non-sugars of an unpurified raw juice, with sulfur dioxide to in crease thehydrogen ion conctration thereof and to render non-sugars insoluble, centriilu= gally separating the insoluble non-sugars from the unheated acidified juice and then liming the juices to render remaining nonsugars insoluble.

6. The process of freeing sugar juices from are no r

non-sugars therein which inclurles acidifying an unlimed raw sugar juice Which contains substantially all of the non-sugars of an unpurified raw juice, with sulfur dioxide until the juice contains about 0.05 milligrams of free sulfur dioxide per liter to increase the hydrogen ion concentration thereof and to render non-sugars insoluble, centrifugally separating the insoluble non-sugars from the unheated acidified juice and then liming the juices to render remaining non-sugars insoluble.

In testimony whereof I afiix my signature.

i JOHN P. FOSTER. 

